The supermarket bread aisle is packed with hearty-sounding multi-grain and wheat varieties. But many of them aren't much more than dressed up white bread.

Bread makers use food coloring, brown wrappers and healthful-sounding words like "stone-ground," "cracked-wheat" and "multi-grain" to make their breads sound more nutritious than they really are. As a result, figuring out which breads are best can be...